Known are several techniques for camera calibration, for example, model based camera calibration and ray based camera calibration. In a model based camera calibration a projection and distortion is described by a simple parametric model, which is often only approximately true.
Ray based camera models generally describe a single camera or a multiple camera device based on a number of rays in 3D space. Each ray describes, how a certain 3D world point gets mapped onto a single pixel of an image sensor of the corresponding camera device. As illustrated by FIG. 1, light rays R, each reflected from a corresponding world point, are projected in accordance with the ray based camera model by a camera C to a sensor S.
The ray based camera model is a powerful camera model as it makes no assumption over a type of projection performed by the camera device, that is, the camera is described as a black box. However, existing calibration methods for ray based camera models are either complex and require active targets with perfect geometry or allow only insufficient calibration.
It is thus generally desirable to provide an apparatus and a method for performing a highly accurate calibration for central and non-central imaging systems in an easy manner.